Spectral device

Abstract

A spectral device is provided with: a filter having a property of transmitting light of multiple wavelength ranges from a measurement object; a driving means to slide the filter; and a detector to detect an intensity of the light from the measurement object, the light having passed through the filter, the detector to further measure the intensity of the light multiple times sequentially while the driving means slides the filter and thereby obtain multiple pieces of measured data to be used for a calculation of spectral information.

What is claimed is: 
     
       1. A spectral device comprising:
 a filter that changes a spectral transmittance depending on a position, the filter transmitting light of multiple wavelength ranges from a measurement object at any position to make the spectral transmittance allow Hadamard transform spectrometry; 
 a driver means that slides the filter; and 
 a detector to detect an intensity of the light from the measurement object, the light having passed through the filter, the detector to further measure the intensity of the light multiple times sequentially while the driver means slides the filter, thereby obtaining multiple pieces of measured data, and calculate spectral information by Hadamard transform on the basis of the multiple pieces of the measured data, 
 wherein the filter has at any position, within a measurement target wavelength region of the detector, two or more discrete wavelength ranges with an 80-percent or more transmittance and three or more discrete wavelength ranges with a 20-percent or less transmittance at any position, the two or more discrete wavelength ranges with an 80-percent or more transmittance being the multiple wavelength ranges that are transmitted by the filter. 
 
     
     
       2. The spectral device as recited in  claim 1 , wherein the detector is a two-dimensional sensor, the spectral device further comprising:
 an objective optical system to form a first image of a measurement target surface on the filter; and 
 a relay optical system to form a second image on the two-dimensional sensor with the light having passed through the filter. 
 
     
     
       3. The spectral device as recited in  claim 1 , wherein the filter includes a multilayer dielectric filter layer with a thickness that increases non-linearly in a direction that the filter slides. 
     
     
       4. The spectral device as recited in  claim 1 , wherein the driver means moves the filter by a predetermined amount each time the detector measures the intensity of the light so that a pseudo wavelength changes at a constant pitch, the pseudo wavelength being a logarithmically transformed wavelength. 
     
     
       5. A spectral measurement data obtaining method comprising the steps of:
 sliding a filter that changes a spectral transmittance depending on a position, the filter transmitting light of multiple wavelength ranges from a measurement object at any position to make the spectral transmittance allow Hadamard transform spectrometry, 
 measuring, by a detector, an intensity of light from a measurement object multiple times sequentially while the filter is slid, the light having passed through the filter, whereby the detector obtains multiple pieces of measured data, and 
 calculating spectral information by Hadamard transform on the basis of the multiple pieces of the measured data, 
 wherein the filter has at any position, within a measurement target wavelength region of the detector, two or more discrete wavelength ranges with an 80-percent or more transmittance and three or more discrete wavelength ranges with a 20-percent or less transmittance at any position, the two or more discrete wavelength ranges with an 80-percent or more transmittance being the multiple wavelength ranges that are transmitted by the filter. 
 
     
     
       6. The spectral measurement data obtaining method as recited in  claim 5 ,
 wherein the detector is a two-dimensional sensor, 
 wherein an objective optical system forms a first image of a measurement target surface on the filter; and 
 wherein a relay optical system forms a second image on the two-dimensional sensor with the light having passed through the filter. 
 
     
     
       7. The spectral measurement data obtaining method as recited in  claim 5 , wherein the filter includes a multilayer dielectric filter layer with a thickness that increases non-linearly in a direction that the filter slides. 
     
     
       8. The spectral measurement data obtaining method as recited in  claim 5 , wherein the filter is slid by a predetermined amount each time the detector measures the intensity of the light so that a pseudo wavelength changes at a constant pitch, the pseudo wavelength being a logarithmically transformed wavelength.